1. Field of the Invention
The present invention relates to a friction clutch mounted in a transmission case or the like and connected between a drive shaft for receiving engine power and a driven shaft for receiving power from the drive shaft and transmitting the power to a power takeoff shaft, and more particularly to a friction clutch having a brake mechanism for preventing inertial rotation of the driven shaft.
.2 Description of the Related Art
A conventional friction clutch, particularly a hydraulically operable friction clutch, used on a tractor or the like includes a first sleeve connected to a drive shaft, a second sleeve connected to a driven shaft, and a friction disk assembly having a plurality of friction disks mounted between the first sleeve and second sleeve. The friction disk assembly is switchable between a clutching state to enable power transmission between the first sleeve and second sleeve, and a declutching state to disable the power transmission. The friction clutch further includes a clutch piston movable between a first position to place the friction disk assembly in the clutching state, and a second position to place the friction disk assembly in the declutching state.
It is necessary to prohibit inertial rotation occurring in this type of hydraulically operable friction clutch, in order to avoid the inconvenience of an external working implement continuing to rotate by inertia when the hydraulic clutch is disengaged. For this purpose, proposals have been made in U.S. Pat. No. 4,751,989 and European Patent Publication No. 0 389 957 to provide a brake mechanism for the friction clutch. This brake mechanism uses a biasing spring acting in a direction to disengage the clutch, which presses a driven-side member of the clutch against a member fixed to the transmission case, thereby to brake the clutch.
The prior construction for pressing the driven-side member against the fixed member to brake the clutch is capable of checking the inertial rotation noted above. However, the driven side of the clutch is locked against rotation. Normally, this type of clutch is maintained in a disengaged state when the engine is switched off, with the result that the driven side is maintained unrotatable. Where, for example, a change speed gear mechanism is disposed downstream of the hydraulic clutch, a shifting operation may be impossible as long as the brake mechanism is in operation. Further, when an external working implement is connected to the tractor, engaging projections formed at selected intervals circumferentially of a power takeoff shaft (PTO shaft) may be out of phase with engaging recesses formed in a power input shaft of the working implement. The above prior clutch construction encumbers an operation to engage the projections and recesses in such a situation. Moreover, it is impossible to engage the projections and recesses if the working implement connected is the type having a power input section thereof not rotatable relative to the power takeoff shaft (PTO shaft) when the working implement is in contact with the ground.